[llvm] r179808 - Set the compact unwind encoding to 'requires EH DWARF' if we cannot generate a CU encoding.

[Bill Wendling]

These two fixes don't really have much in the way of testcases that I can add... I.e., these should be edge cases if there at all. But I'll try my best...

-bw

On Apr 18, 2013, at 4:01 PM, Eric Christopher <echristo at gmail.com> wrote:

> Testcase? ;)
> 
> -eric
> 
> On Thu, Apr 18, 2013 at 3:55 PM, Bill Wendling <isanbard at gmail.com> wrote:
>> Author: void
>> Date: Thu Apr 18 17:55:29 2013
>> New Revision: 179808
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=179808&view=rev
>> Log:
>> Set the compact unwind encoding to 'requires EH DWARF' if we cannot generate a CU encoding.
>> 
>> Modified:
>>    llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
>> 
>> Modified: llvm/trunk/lib/Target/X86/X86FrameLowering.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86FrameLowering.cpp?rev=179808&r1=179807&r2=179808&view=diff
>> ==============================================================================
>> --- llvm/trunk/lib/Target/X86/X86FrameLowering.cpp (original)
>> +++ llvm/trunk/lib/Target/X86/X86FrameLowering.cpp Thu Apr 18 17:55:29 2013
>> @@ -528,11 +528,11 @@ uint32_t X86FrameLowering::getCompactUnw
>>     if (!MI.getFlag(MachineInstr::FrameSetup)) break;
>> 
>>     // We don't exect any more prolog instructions.
>> -    if (ExpectEnd) return 0;
>> +    if (ExpectEnd) return 0x04000000;
>> 
>>     if (Opc == PushInstr) {
>>       // If there are too many saved registers, we cannot use compact encoding.
>> -      if (SavedRegIdx >= CU_NUM_SAVED_REGS) return 0;
>> +      if (SavedRegIdx >= CU_NUM_SAVED_REGS) return 0x04000000;
>> 
>>       SavedRegs[SavedRegIdx++] = MI.getOperand(0).getReg();
>>       StackAdjust += OffsetSize;
>> @@ -542,7 +542,7 @@ uint32_t X86FrameLowering::getCompactUnw
>>       unsigned DstReg = MI.getOperand(0).getReg();
>> 
>>       if (DstReg != FramePtr || SrcReg != StackPtr)
>> -        return 0;
>> +        return 0x04000000;
>> 
>>       StackAdjust = 0;
>>       memset(SavedRegs, 0, sizeof(SavedRegs));
>> @@ -552,7 +552,7 @@ uint32_t X86FrameLowering::getCompactUnw
>>                Opc == X86::SUB32ri || Opc == X86::SUB32ri8) {
>>       if (StackSize)
>>         // We already have a stack size.
>> -        return 0;
>> +        return 0x04000000;
>> 
>>       if (!MI.getOperand(0).isReg() ||
>>           MI.getOperand(0).getReg() != MI.getOperand(1).getReg() ||
>> @@ -560,7 +560,7 @@ uint32_t X86FrameLowering::getCompactUnw
>>         // We need this to be a stack adjustment pointer. Something like:
>>         //
>>         //   %RSP<def> = SUB64ri8 %RSP, 48
>> -        return 0;
>> +        return 0x04000000;
>> 
>>       StackSize = MI.getOperand(2).getImm() / StackDivide;
>>       SubtractInstrIdx += InstrOffset;
>> @@ -574,11 +574,11 @@ uint32_t X86FrameLowering::getCompactUnw
>>   if (HasFP) {
>>     if ((StackAdjust & 0xFF) != StackAdjust)
>>       // Offset was too big for compact encoding.
>> -      return 0;
>> +      return 0x04000000;
>> 
>>     // Get the encoding of the saved registers when we have a frame pointer.
>>     uint32_t RegEnc = encodeCompactUnwindRegistersWithFrame(SavedRegs, Is64Bit);
>> -    if (RegEnc == ~0U) return 0;
>> +    if (RegEnc == ~0U) return 0x04000000;
>> 
>>     CompactUnwindEncoding |= 0x01000000;
>>     CompactUnwindEncoding |= (StackAdjust & 0xFF) << 16;
>> @@ -595,7 +595,7 @@ uint32_t X86FrameLowering::getCompactUnw
>>     } else {
>>       if ((StackAdjust & 0x7) != StackAdjust)
>>         // The extra stack adjustments are too big for us to handle.
>> -        return 0;
>> +        return 0x04000000;
>> 
>>       // Frameless stack with an offset too large for us to encode compactly.
>>       CompactUnwindEncoding |= 0x03000000;
>> @@ -616,7 +616,7 @@ uint32_t X86FrameLowering::getCompactUnw
>>     uint32_t RegEnc =
>>       encodeCompactUnwindRegistersWithoutFrame(SavedRegs, SavedRegIdx,
>>                                                Is64Bit);
>> -    if (RegEnc == ~0U) return 0;
>> +    if (RegEnc == ~0U) return 0x04000000;
>> 
>>     // Encode the register encoding.
>>     CompactUnwindEncoding |= RegEnc & 0x3FF;
>> 
>> 
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